The above photo, shows the snapshot of the iTunes Error 40, occurred on iPhone. The error 40, sucks a lot, you would probably be annoyed with this and confuse, how to fix error 4o on iPad, iPhone or iPod Touch and get rid of it. Hey folks, don’t be panic and worry, i have got an easy fix for iTunes Error 40 and believe me you can fix this error in seconds. Before we get into the topic of fixing error, let us talk, why you are getting this error? After upgrading to iOS 6, you may have notice many different iTunes errors as well rather than this one. This problem usually occurs, when you restore to a firmware, that is actually not verified on Apple server, Apple block these firmwares that are not signed, due to this iTunes may give you error 40.
Step by Step Instructions to Fix iTunes Error 40
Step 1. First of all navigate the Host file from this location on your Windows:
Step 2. Now Right click on the Host file, and open it in Notepad.
Step 3. Now Remove the links and leave the rest as you can see in the below image; it will clear your concept
Related: Fix iTunes error 3194
Step 4. Once edit as like the above shown in the image, save it and close the Notepad.
Step 5. Now you can connect your device to iTunes and Restore your device normally by just hitting the Shift Key+ Click on Restore and select IPSW file for your device you want to Restore to.
The above method should work 100%, but if in any case it did not, then Download this custom host file and replace it with one in C:\Windows\System32\drivers\etc directory. [Download Link to Host File]. This should work. Hope so it working for you, in case you have confusion at any step, feel free to ask in the comment box.